Mike Edwards, managing director of Innovention Consultancy, discusses the effective use of heat and water.
Few of us are lucky enough to run laundries located on windswept islands, adjacent to a fast flowing freshwater river, or where the sun shines 10 hours a day.
With a combination of solar, wind and hydropower, coupled with boreholes, total water recycling or seawater desalination, we would be able to achieve true sustainability, where the essential resources that we need are being constantly replaced.
Back in the real world this is an impossible dream – our best shot at sustainability is to minimise our primary consumption of water and energy and recycle as much as possible for reuse.
I would like to tackle just one aspect that applies to every laundry, drawing on my company’s four-decade developments and applications as they apply to the waste heat and water that is the result of the process of washing. You may find the conclusion surprising.
The lower the washing temperature, the less energy you use, right? Wrong. Imagine that you currently wash in your CBW at 65°C followed by the standard cold rinse. If you measure the temperature of the mixed wastewater, in a plant processing one tonne of linen per hour the result could be 6,000 litres per hour going to drain at 45°C Essentially you have heated six tonnes of water from the incoming main at 10°C, and then thrown away that same six tonnes at a temperature of 45°C. That’s roughly 243kW in one hour.
Now suppose that you decide to increase your budget for chemicals and introduce a ‘low-temperature washing system’. The wash temperature in the CBW now becomes 50°C and the temperature to drain drops to 35°C. That means that you are now throwing away 173kW per hour, around 28 per cent less than before. The final rinse temperature will also have dropped a few degrees, perhaps to around 23 to 25°C so you can expect the normal production clogging drying times for towelling etc.
Now take the Aquatherm approach, go back to low-cost chemistry but increase the wash temperature to 75°C or higher. The wastewater will now exit the machine at a mixed temperature of around 55°C. Incoming cold freshwater at 10°C is then preheated by the energy extracted from the wastewater, and now feeds into the rinse end of the machine at around 45°C, which with the carryover of heat from the wash section will rise to 50°C prior to pressing/extraction and then drying.
Meanwhile the wastewater, having had its energy largely extracted, will go to the final drain at 20°C or under, a net loss of 70 kW or 71 per cent less than the original process. Any plant study into sustainability must focus on what is being sent to waste, be it through hot water or hot air. What you keep in the building does not need to be replaced; this is the Holy Grail of energy reduction. Meanwhile, with all this recycled heat to play with in the CBW, hot rinsing improves quality, reduces process time and makes significant inroads into drying times. It is not unusual to see fully dried category drying times cut from 20 to 15 minutes, with a corresponding reduction in steam or gas consumption.
This is just one aspect of a complex topic, which when combined with water reuse and carefully matched with suitable chemistry highlights a significant opportunity to change the way that we operate in the laundry industry, to the benefit of the environment and the business itself.